Parallel Optical Processors and Memories

POPAM - 6863

Work Area: Novel Concepts and New Materials for Optical Devices / All-Optical Computing

Keywords parallel optoelectronics, holographic memories, optical interconnections, diffractive optics, dynamic holography, spatial light modulators

Start Date: 1 November 92 / Duration: 36 months / Status: running

[ participants / contact ]

Abstract POPAM is developing devices and materials for parallel optoelectronic system applications. The devices are being integrated into a holographic memory demonstrator that is reconfigurable with high storage capacity and fast access and which can be dynamically updated. The memory will test the scaleablity, compactness and integration of the device technologies.


Parallel optoelectronics may offer solutions to data flow bottlenecks that arise in applications such as in telecommunication and computer networks, memories and recognition systems. The aim of POPAM is to demonstrate the scaleablity, compactness and integrability potential of parallel optoelectronics technologies in the context of an updatable holographic memory.

Approach and Methods

The consortium brings together complementary skills in optical information processing systems, diffractive optics, spatial light modulators, and real time holographic devices and materials.

A holographic memory is being implemented that is reconfigurable with a high storage capacity and fast access. Dynamic updating will be achieved by adding a feedback loop. The optical components needed are being studied and developed within the project.

The formatting and manipulation of information in the form of optical beamlet arrays is being achieved using computer generated holograms in conjunction with spatial light modulators and real time holograms. Existing masking and etching facilities for the fabrication of computer generated holograms are being improved and direct excimer laser micromachining of components investigated. A novel high resolution optically addressed spatial light modulator is being developed and bacteriorhodopsin is being studied as an alternative to the photorefractive materials used in the demonstrator.

Progress and Results

A basic dynamic memory system has been designed and built. Several images have been stored in a photorefractive crystal and recalled at high speed using a phase encoded reference beam. The phase encoded reference beam is derived using a custom spatial light modulator illuminated by an diffractive optical array generator produced within the project. The demonstrator is being refined as optimised components become available to the project.

Procedures for fabricating diffractive optical elements by electron beam lithography and reactive ion etching are continuously being improved and the first trials of replication by excimer machining are taking place. High quality bacteriorhodopsin films have been prepared. The potential use of their strong nonlinear optical properties to provide the non-linear functions needed in the memory is being assessed. Progress is also being made on photorefractive image amplifiers and on the design and fabrication of an optically addressed spatial light modulator which may find use in all optical approaches to dynamic memory refreshing.


The knowledge gained from the device and system development will allow the assessment of the potential for densely interconnected compact parallel optoelectronic solutions to information processing problems. Opportunities exist for spin-offs in communications network space switching, pattern recognition and neurocomputing hardware.

Latest Publications

Information Dissemination Activies

Presentations have been given on `Optical Memory and Optical Data Storage' (ISOM/ODS'93), `Photorefractive Materials' SPIE-San Diego '93,`Physique des systemes de traitement optique de l'infirmation', SFP '93, Toulouse and `Phase conjugation and amplification due to two wave interaction in photorefractive BaTiO3', PRM '93, Kiev.


Kings's College London - UK
Physics Department
The Strand


Technische Hochschule Darmstadt - D
Ris_ National Laboratory - DK
Thomson-CSF - F
Forth Research Centre Crete - GR


Dr. T.J. Hall
tel +44/71-873-2151
fax +44/71-836-1799

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POPAM - 6863, August 1994

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html version of synopsis by Nick Cook